My invention relates to a muting circuit, and particularly to a muting circuit for preventing data signals from being audibly reproduced by a radio receiver.
In radio communication systems, data signals are frequently transmitted just before voice signals. Such data signals provide identification or other functions, and are desirable or sometimes necessary. However, if the data signals are audibly reproduced by the radio receiver, they are noisy and can be annoying to a person operating or using the receiver, particularly over long periods of time.
Accordingly, a primary object of my invention is to provide a new and improved muting circuit for radio receivers.
Another object of my invention is to provide a new and improved circuit that provides a muting signal in response to received data signals.
Another object of my invention is to provide a new and improved circuit that provides a muting signal in response to data signals having a relatively steady or constant rate.
Another object of my invention is to provide a new and improved circuit that provides a muting signal when a radio receiver receives data signals, and that provides no muting signals when a radio receiver receives relatively random signals such as voice or noise.
Data muting circuits for radio receivers are known in the art, such as exemplified by U.S. Pat. No. 3,939,431. However, such known muting circuits suffer from various disadvantages. Thus, the circuit shown in U.S. Pat. No. 3,939,431 uses timers which have a predetermined time period. If the data signals have a different time period or frequency, the timers will not respond and hence the muting circuits will not function.
Accordingly, another object of my invention is to provide a new and improved muting circuit which can respond to or function with data signals whose frequency need not be predetermined, but may be any relatively constant frequency.